1. Technical Field
The present invention is generally directed to data or information storage systems where a sensor and/or write element is disposed in proximity to a storage medium which is moving relatively to the sensor and/or write element. More particularly, the invention deals with magnetical or optical storage devices. Still more specifically, the invention relates to a method and apparatus for determining temperature and a temperature distribution in a slider on the storage device.
2. Description of the Related Art
A hard disk drive (HDD) is a digital data storage device that writes and reads data via magnetization changes of a magnetic storage disk along concentric tracks. During operation of the HDD, the magnetic storage disk is rotated at speeds in the order of several thousand revolutions-per-minute (RPM) while digital information is written to or read from its surface by one or more magnetic transducers. To perform an access request, the HDD first positions the sensor and/or write head, also referred to as xe2x80x9cread/write head,xe2x80x9d at the center of the specified data track of the rotating disk.
During operation of the HDD, the read/write head generally rides above the disk surface on a cushion of air, caused by an xe2x80x9cair bearing surfacexe2x80x9d, that is created by the movement of the disk under the head. The distance between the read/write head and the disk surface while riding, or partially riding, on the air cushion is referred to as the xe2x80x9cflying heightxe2x80x9d of the head.
Further, the head is carried by a xe2x80x9csliderxe2x80x9d which is supported by hydrodynamic lift and sink forces. These lift forces are given by the interaction of air streaming underneath the surface structure of the slider. The slider itself is mounted to a flexure (gimbal) which is a part of a suspension well-known in the prior art. The suspension includes a load beam having a mounting region on a proximal end, the flexure on a distal end, a relatively rigid region adjacent to the flexure and a spring region between the mounting region and the rigid region. The mounting region is typically attached to a base plate for mounting the load beam to an actuator. A motor, e.g. a voice coil motor, which is controlled by a servo control system moves the actuator arm to position the read/write head at desired information tracks on the disk.
The performance of the HDD in general depends, to a great extent, on the maintenance of an exact head position versus the disk surface during a reading or writing process. Today, the flying height is as small as 10 nm and is expected to decrease by a factor of two within the next two years. Higher data capacities will lead to read/write heads near contact to the recording medium. Even recording schemes by using contact recording are being considered.
Lowering the flying height improves the performance of the HDD, but partial mechanical contact or friction between the slider and spinning disks, which do not have ideal smooth surfaces, is playing an increasing role in terms of heat generation. While decreasing the flying height, these additional friction forces increase the temperature of the slider as well as that of the rotating medium.
The temperature and temperature distribution in the slider and the read/write head have an influence on HDD performance. First, both the (magnetic) read and write functions of the head and disk have certain temperature-dependent characteristics. Second, the distance of a slider from a spinning disk depends on the ambient temperature. Increasing the ambient temperature increases the temperature of the slider. It has been shown recently that heating the slider body changes the flying height, due to a deformation of the slider influencing the air-bearing surface (cf. P. Mxc3xa4chtle et al.; xe2x80x9cIntegrated Microheaters for in-situ Flying Height Control of Sliders used in HDDs,xe2x80x9d Conf. Proceedings MEMS 2001, Interlaken (CH), Jan. 21, -Jan. 25, 2001; to be published).
Thus, a control of the local temperature and the temperature distribution would allow an improvement of the HDD performance. Accordingly, a need exists to determine the temperature and the temperature distribution of a slider and the read/write element.
It is therefore an object of the present invention to provide a method for determining the temperature and the temperature distribution in a slider.
It is another object of the present invention to provide such a method that can be performed in-situ, i.e., while the slider is positioned over a spinning disk.
It is still another object of the present invention to provide an apparatus that is able to carry out such a determination method.
In one embodiment of the present invention, a measurement of a temperature and/or temperature distribution within a slider due to local heat transfer is provided, whereby the slider is positioned above the surface of a rotating disk, and carries a sensor and/or write element, whereby the rotating disk is moving relatively to the sensor and/or write element, and whereby the shape of said slider is changed locally due to the temperature and/or temperature distribution. By measuring the shape changes of the slider, the temperature and/or temperature distribution can be calculated on the basis of the changes by means of numerical methods. The method may be used as an in-situ measurement in already existing testers, like, e.g., flying height testers. No additional hardware is required and studies of the slider near contact can be performed. In addition, information with respect to the flight height is obtained simultaneously.
These and other objects and advantages are achieved by the method and system disclosed and claimed in the present patent.